Tough nanopaper structures based on cellulose nanofibers and carbon nanotubes

Carbon nanotube (CNT) nanocomposites based on CNT in a polymer matrix typically have low strain to failure in tensile loading. Furthermore, mixing of more than a few percent of CNT with either molten thermoplastics or monomers in bulk often results in agglomeration of CNT. Here, multiwalled CNT (MWCNT) are mixed with nanofibrillated cellulose (NFC) in aqueous suspension and filtered into tough nanopaper structures with up to 17 wt% of MWCNT commingled with NFC nanofibrils. Carbon nanotubes were surface treated with a surfactant, and homogenous suspensions of carbon nanotubes in water miscible with the NFC suspension was obtained. NFC/CNT nanopaper structures were characterized for porosity using mercury displacement, and studied by FE-SEM and AFM. Mechanical properties were tested in uniaxial tension and electrical conductivity was measured. The processing route is environmentally friendly and leads to well-mixed structures. Thin coatings as well as thicker films can be prepared, which show a combination of high electrical conductivity, flexibility in bending and high tensile strength.